The present invention relates to an electrical test probe tip for use with testing instruments, and more particularly to an electrical test probe flexible coil or spring tip.
An electrical test probe generally consists of a probing head with a tip, a cable, and a connector for attaching the cable to test instruments. The probing head may have an integral or replaceable probing tip that is suitable for making an electrical contact with electrical components. The probing head is attached to a first end of the cable and the test instrument connector is attached to the opposite end of the cable. A means for connecting the probing head to ground is also generally included in the probing head. Ground provides the electrical reference point for other signal measurements, so the ground connection typically remains unchanged while the probing head is moved around to make signal measurements.
Electrical test probes are used to provide an electrical connection between electrical components and testing instruments such as oscilloscopes and other measuring, monitoring, diagnostic, and signal processing instruments. As shown in FIG. 1, a traditional test probe tip is an elongate conductive member that terminates in a conical, blunt, or rounded point.
When a test probe contacts a pin or lead on an electrical device to be tested, it forms an electrical connection therewith. The electrical signal on the pin may then be measured, monitored, or otherwise processed. It is difficult to form a contact with a single pin on a modem integrated circuit chip (“IC”) with a traditional test probe tip because miniaturization has resulted in close spacing of the pins. If two adjacent pins are contacted simultaneously by the test probe tip, a short circuit may result between the two adjacent pins. A short circuit may prevent measurement of the desired signal and may result in damage to the internal circuitry of the IC. A traditional test probe tip provides no means for preventing the occurrence of a short circuit.
IC grabber probes that enable connection to small IC legs or small connection points are well known. These grabber probes have a jaw-like tip that connects and holds a pin. These grabber probes, however, are relatively stiff and prevent optimum positioning of probing heads.
Tektronix produces a signal-ground adapter that has been specifically designed to connect with a square pin. But like the IC grabber probes, the signal-ground adapter connects rigidly to signal and ground pins, and the inflexibility prevents desirable movement of the probing head to optimum positions. Tektronix also produces a right-angle adapter that includes a stiff coil used to rigidly attach a probe at a right angle to a pin. The purpose of the stiff coil is to mate with a pin, and the stiffness prevents movement of the probe. Because it is inflexible after mating with the pin, the coil is not adaptable and may be used in only one position for probing a specific type of pin (a 0.025 inch diameter square pin). Tektronix also produces a “Y-lead” adapter having wire leads that may be combined with the right-angle adapter. The combination of the right-angle adapter and the Y-lead adapter may allow the probing head to be moved relative to the device being probed, but the addition of leads may add inductance. Probing an electrical device using the Y-lead adapter may be inconvenient or impossible, using just one hand. Typically, the probe body must be laid on the table while pin connections are changed. Draping the wire leads on electrical components and moving parts, such as a CPU fan, is another disadvantage of the Y-lead adapter.
Several prior art references are directed to electrical test probe tips and electrical connectors. U.S. Pat. No. 4,978,312 to Fodali (the “Fodali reference”) is directed to a tip attachment for a circuit test probe and, specifically, to a spring attachment for placement on a handheld tester with an ice pick type probe. One end of the tapered spring tip attachment fits on the ice pick type probe, and the other end terminates in a straight length of wire. The purpose of this spring attachment is to provide a smaller gauge tip for insertion into sockets too small for the ice pick probe. In other words, the Fodali tip uses a spring merely as a connector for attaching the straight wire probe end to a tapered ice pick type probe.
U.S. Pat. No. 3,885,848 to Brouneus (the “Brouneus reference”) is directed to a method of making an electrical connection with a flat surface contact using a conical spring. The contact member is a conically spiraled length of electrically conductive resilient wire including spirals which progressively increase in size. A cylindrical helix is electrically connected to the small end of the volute helix. An electrically conductive terminal member may be inserted into and secured within the cylindrical helix. The wide end of the conical spring may be electrically connected to a flat conductive surface. Compressing the volute helix moves the spirals of the helix into contact with a flat surface.